This invention relates to nonlinear circuits for driving inductive loads and in particular to a boost voltage generator for use in a fuel injection system of an internal combustion engine.
Previous circuits for injectors for internal combustion engines utilized linear solenoid driving circuits to generate and deliver a rapid change in the rise current of a coil of a solenoid valve associated with a fuel injector. These linear driver circuits and/or systems used feedback techniques to control the level of injector current and often employed a boost voltage network to produce an increased voltage level that periodically overdrove the injector coil. These prior systems work adequately, however, they are often characterized as having high power consumption. In addition, large enclosures are often associated with these systems since it is necessary to dissipate the excess heat generated. The present invention offers a solution to the above problems by providing a driver circuit which functions in a switching mode of operation.
Accordingly, the invention comprises:
A pulsed switching type boost voltage generator responsive to a pull-in signal for generating and for storing a boost voltage signal in excess of the voltage established by a battery in synchronism with the generation of the pull-in pulse.
The circuitry utilizes comparator circuits throughout to lessen the requirement for accurate gain control and accurate amplifier offsets. A feature of the present invention is the incorporation therein of means to adapt its operation in correspondence with the variation of battery voltage and temperature thereby maintaining a uniform output over wide ranging conditions.
Many other objects, features and purposes of the present invention will become clear from the following detailed description of the drawings.